Method of treating fibrous web material



Patented Jan. 11, 1944 METHOD OF TREATING FIBROUS MATERIAL I WEB Lloyd L. Dodge, Wausau, Wis assignor to National Paper and Chemical Company, Wausau, Wis., a corporation of Wisconsin No Drawing. Application December 11, 1939, Serial No. 308,667

3 Claims.

This invention relates to the treatment of paper and like fibrous web material to enhance the desirable properties thereof, such as its wet strength, its resistance to penetration by moisture, grease and gases, and its resistance to alkali, acids and alcohol.

I have now found that the wet strength and other desirable properties of paper and similar fibrous web material can be materially increased by treating such paper and the like with an aqueous dispersion of a casein, a wax and a plasticizer, incorporating a methylene hardening agent into the treating composition and drying the treated paper or the like at an elevated temperature to harden the casein and fuse the particles of wax over the fibers. The treatment can suitably be effected during the course of manufacture of the fibrous web material, as by coating, spraying, immersing, or other form of application. Subsequent drying of the treated web on the usual driers of a paper machine, board machine or the like, is sufficient to give a finished product having the desirable properties above mentioned.

It is therefore an important object of this invention to provide a composition for application to paper and like fibrous web material for the purpose of increasing the wet strength of the paper, or enhancing other desirable properties such as those above enumerated.

It is a further important object of this invention to provide a method whereby paper and like fibrous web material, during the course of its manufacture, can be treated with an aqueous dispersion of a casein, wax, plasticizer and methylene hardening agent to increase its wet strength and impart other desirable properties to the fibrous web material.

It is a further important object of this invention to provide paper and other like material having increased wet strength and other desirable properties due to the treatment thereof with a composition including a hardened casein, a wax and a plasticizer.

Other and further important objects of this invention will become apparent from the following decription and appended claims.

As already stated, the treating composition of my invention includes a casein, a wax and a plasticizer for paper, or cellulose fibers. The casein may be either a milk casein or a vegetable casein, such as may be obtained from oleaginous seeds. Animal protein is not satisfactory for my purpose. The term casein is therefore used in a generic sense to include both milk and vegetable ticles in the emulsion have a maximum diamhave found to be suitable, polyhydric alcohols,

such as glycerol and the water soluble glycols, sugars, deliquescent salts, and the like, may be mentioned. A preferred plasticizing composition is prepared from 1 part of glycerol and 2 parts of corn sugar by weight. The lasticizer is primarily selected because of its ability to plasticize the fibers and not for the purpose of plasticizing the casein, although the latter is also realized.

The following will serve to illustrate a preferred embodiment of my invention, parts by weight r being given except where otherwise specified:

Example To parts of casein are added 500 parts of Water containing 5 parts of dissolved borax. The aqueous mass is heated to F. and stirred until it clear dispersion of the casein is obtained. There are then added 25 parts of a plasticizer comprising a mixture of glycerol and corn sugar, 10 parts of the previously described wax emulsion having a 50% solid content, and 5 parts of a 6% aqueous solution of formaldehyde. After the mixture has been thoroughly agitated and a uniform dispersion obtained, it may suitably be diluted with an equal volume of water before use. Such dilution brings the solid content. from about 14% to about 7%.

A considerable variation in the proportions. of i casein.

tween 2"and 25% by weight of the casein, and the proportion of plasticizer between and 100% by weight of the casein. By increasing the proportion of wax, greater transparency is obtained in the final sheet. t

In. place of borax, any suitable alkaline substance may' be used for the dispersion of the If soybeancasein, or soybean flour be substituted for animal casein, a somewhat higher degree of alkalinity is necessary to effect a uni-- form dispersion of the vegetable caseins and for thispurpose caustic alkali, either by itself or.

withza small proportion maybe used.

The amount of formaldehyde may also be varof calcium hydroxide,

ied, depending upon the degree to which the casein is to be hardened or insolubilized. Other methylene hardening agents, such as hexamethylene tetramine, may be used in place of formaldehyde, or polymers of formaldehyde may be used. Instead of incorporating the methylene hardening agent directly in the aqueous treating composition, the fibrous material, after treatment with the aqueous emulsion, may be subjected to formaldehyde gases. It is preferable to incorporate the formaldehyde into the aqueous treating composition need be applied only to one side of. the sheet to effect a thorough impregnation thereon/The treated paper has a greatly increased wet strength and is relatively moisture-,

ing composition just prior to its use, since otherwise coagulation is likely to take place.

Inthe treatment of paper on the paper ma- I chine to increase its wet strength, the aqueous treating composition may best be applied at a size press intermediate sections of the driers at which point the moisture content of the sheet is less than Either one or both sides of the paper may be contacted with the aqueous treating composition. 'The treated paper is then run immediately over the driers beyond the point of application of the aqueous treating composition to dry the paper quickly, insolubilize the casein and cause the wax to fuse over the fibers of the paper. The penetration of the wax into the paper is very slight, but the plasticizer, being water soluble, penetrates quickly and completely into the body of the sheet.

While my invention is applicable to various kinds and weights of paper, as well as to paper board and the like, it finds particular application in the case of light weight wrapping papers,

vegetable parchment and the like, for use, in the wrapping of fats, such as lard, candies, and the like.

By way of example, if a paper of 30 lbs. basis weight per ream of 500 sheets, each 24 x 36 inches, is treated in accordance with the method just described, the increase in weight due to retained solids is approximately 1 lb. per ream. The. sheet becomes much more dense, the pin holes being largely closed by the retained solids, and

' the openness of such a sheet, the aqueous treatgreaseand gas-proof-despite the comparatively open formation of the sheet itself. Light weight, wrapping papers of kraft pulp as well as sulphite pulp may be treated in'this manner.

One of the important features of my invention is the incorporation of the plasticizer in the casein-wax emulsion, since this is largely responsible for the superiority of my coating composition. The grease-proofness of the paper due to the casein-wax content is not adversely affected by the presence of'the plasticizer, while the paper is thoroughly plasticized. Ordinary wax coatings are likely to 'be broken by severe creasing,

thereby destroying or greatly reducing the grease-proofness of the coated'sheet. In the case of my plasticized, casein-wax coated paper, creasing of the coated paper, has no such effect since the coating remains intact. The same result is not obtained by separately plasticizing the body of the fibrous web material and then applying an unplasticized casein-wax coating thereover.

It will, of course, be understood that various details of the process may be varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. In a method of making paper comprising the steps of forming a wet paper web and heating the web to dry the same, the improvement including simultaneously applying to said wet paper web a coating of an aqueous dispersion of a protein selected from the class consisting of casein and the water insoluble proteins naturally present in oleaginous seed material, paraflin wax, a plasticizer and a methylene containing hardening agent, whereby said web on subsequent heating is rendered stronger and more proof to moisture, grease and gas due to resulting hardening gf the protein and fusion of the wax on the paper bers;

2. In a method of making paper comprising the steps of forming a wet paper web and heating the web to dry the same, the improvment includweb a coating of an aqueous'dispersion of soya bean protein, paraflln wax, a plasticizer and a methylene containing hardening agent, whereby said web on subsequent heating is rendered stronger and more proof to moisture, grease and gas due to resulting hardening of the soya bean protein and fusion of the wax on the paper fibers.

3. In a method of making paper comprising the steps of forming a wet paper web and heating the web to dry the same, the improvement ineluding simultaneously applying to said wet paper web a coating of an aqueous dispersing of casein, paraffin wax, a plasticizer and a methylene containing hardening agent, whereby said web on subsequent hardening is rendered stronger and more proof to moisture, grease and gas due to resulting hardening of the casein and fusion of the wax on the paper fibers.

LLOYD L. DODGE. 

